我得到了nasm，我想将程序集编译成可执行文件。我不断收到错误：
ld: warning: ignoring file firststart.asm, file was built for unsupported file format which is not the architecture being linked (x86_64)
Undefined symbols for architecture x86_64:
"_main", referenced from:
start in crt1.10.6.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
当我尝试用 gcc 编译时。我正在使用 xcode 附带的 gcc。我究竟做错了什么？